Process of tannng skins and hides.



- Alsace, Germany,

of the skin 'UNITED STATES PATENT OFFICE.

.. nanny sum,

or MiITLHAUSEE-GEBMANY, nssrenon TO THE FIRM, or c. H.

:Bonnnmenn'sonn, or manna menm nm, GERMANY.

937,720 f 2R0 Drawing.

To all iplwm 'it my camera: Be it known that. I, HENRY SCHMID,

chemist, a citizen of the Swiss Republic, re-

siding vat Salvatorstrasse, Miilhausen, -m have nvented certain new m-Processes of and useful Improvements of which the fol- Tanning Skins andHides, lowing 1s a specification.

My present invention relates to improvements in the art of tanning skinsand hides by means of metallic oxids, and it has for its objectprimarily to provide an improved process of this character whereby theleather obtained is unusually strong and is capable of being quicklydyed, the metallic oxids being so intimately introduced into the fiberThe methods hitherto known of this kind of tanning and of tawing hidesand skins had in view a combining of the animal skin with ametallic oxidor basic metallic oxid of the formula Me O 'Invchrome tanning, forinstance, the skins are impregnatedwith a basic chromic salt. In the.same. measure as chromic oxid or hydroxid is fixed on the fiber, acid isset .at liberty, for instance ac--. cording 'to the equation wherein asesquioxid-may also be-combined with two oxids MeO, or several. sesuioxids with each other or with a MeQoxi viz or,o +'A1,o,I. or o wam,A1' o,+Fe o, I +Me0 +Me0 +Me0 have affinities for pigments which areunknown or at least-have not been utilized in connection with simpleoxids. They also produce'lakes of greater intensity and higher resistingpower due, it. seems, that the combined oxids adhere more trongly to thefiber and therefore combine with it more intimately. Such binary andSpecification of Letters ZPatent.

as to render them perfectly fast.

I Water,

Such have M to the fact rnoenss or 'rnnnrno sKms AND nrnns.

Patented Oct. 19, 1909.

Application filed December 4, 1907. Serial No. 405,026.

ternary compounds are, for instance, compounds of. the formulae Cr OMgO, and

'Al O MgOZnO. Experiments made with these combined mordants in mineraltanning demonstrate .that a particularly strong leather is obtainablewhich permits an unusually fast dyeing, especially when fastmordant-dyesare employed.

According) to the present" invention the hides may first tanned in theordinary way, for example, with a basic salt of chromium ,oxid such as abasic sulfate or a basic chlorid of chromium, but instead ofneutralizing the acid thus set free by 'means ofborax' or alkalisilicate or the like, as has been said is usual in the known processes,the hide is now treated with the alkaline solution of another'metallicoxid insoluble in tion of sodium zincate Zn(ONa) Thus the followingreaction would take place:

but the whole reaction, including the chromic salt, may be re resentedfor instance by the following equa ion:

for instance, with an aqueous solu- I Thus the soda of the sodiumzincate or'a partof it combines with the portion of the:

acid radical not already neutralized, both 'chromic oxid and zinc oxidbeing set free and ,preci itated simultaneously in the skin. As a resut, a more complete action of the chromic oxid is obtained and, moreover,this chromic'oxid is more intimately combined with and enriched by thezinc oxid,

Xed on the skin or hide than are the simple oxids. By the formation 'ofthis dou 1e dye-lake a more intense, lastingand-deeper coloring iseffected with a smaller quantity i of dye.

Instead of using a sodium zincate solution, other solutions might be.employed wh ch have 'a similar chemical action. For instance, a solutionof aluminate of soda or an ammoniacal solution of copper of chemicallyequivalent quantities might be employed, and in such case thefollowingreaction probably takes place:

Al(ONa)L,-l'-3 HC1=A1(OH) +3 N501. A similar action will takeplace whenusing thecompound thus produced being-more intimately I a solution ofcopper oxid in ammonia, but an exact chemical equation of the reactionwhich takes place in the latter instance cannot be given because suchammoniacal solutions of copper are not of uniform composition. By usingthe turkey red" oils the accordance with my present invention, the

following may serve as an mstance which will enable those skilledintheart to practice the invention. After the skins or hides have beenprepared for tannin that is to say, after they havebeen washed,depilated,

and freed of lime, they are placed in a bath of basic chromic chlorid of1 Baum.

l About every fifteen minutes so much chrome extract is added that theconcentration of the tanning-bath is increased by 250.25 or 0.5 Baumeach time, until it has reached about 3- Baum. By chrome extract ismeant mixtures conslsting chiefly of basic chlorid of chromium-or ofbasic sull fate of chromium or of a mixture of these chrome salts. Suchmixture may also con- 1 I tain chlorid of sodium or. sulfate of sodium,according to the method of preparing the extract; By cutting through aportion of the skin, the condition thereof may be de- "termined, andwhen a "sample cut indicates that the skins are completely tannedthroughout the thickness, they are taken from the bath and transferredto a bath containing a sodium zincate-solution of 2 Baum. Eve

Y 40 20 minutes so much sodium zincate is added that the concentrationof the bath' is increased by 0.5 Baum each time, until it has reached4Bai1m, 80 minutts being 1 {thus required for the treatment; The skins4501' hides are thenwell washed and subsequently worked in. the usualmanner.

The combined use of salts of different I metals such, for, instance, asacetate of aluminium or chromium with those of limevv 50. or magnesia,has been racticed heretofore.

Such prior'processes di er from the present invention in the followingrespects: Ac-

cording to the present invention, basic metallic saltis exposed to theaction of the metallic salt dissolved in caustic alkali; By

the reaction,

1 Cr(OH) ,,+Zn(OH)'(ONa) NaCl, to a thorough and immediatedeacidifica'tion of the basic salt takes lace until an insolublecompound,or a meta lic hydroxid, separates,

and at the same time the oxid dissolved in alkali is set free and isdeposited on the fiber. ofthe skin in'such an intimate rela-'of'metallic salts, which consists in im regtion therewith as to renderit very adhesive. The metallic salts absorbed by the skin are I thusdeacidified and precipitated by means of a suitable alkalinedoublecompound such, for instance, as sodium zincate Zn(ONa) sodium aluminateAl(ONa) and at the same time, the ecipitated oxid, such as Cr(OH) ,,isenrlched by. the oxids which are se arated from the alkaline doublecompoun s. Thesodium aluminate is employed in exactly the same mannerashas been described in the case of sodium zincate. As a result, the oxidsare sointima'tely' embodied in the skin as to render them perfectlyfast, the results being superior to the previous method of neutralizingthe basic salts by an alkali or byinsoluble carbonates such, forinstance, as prepared chalk.

Another advantage obtained by the present invention is, that a largerpercentage of the various metallic oxids is introduced into the fiber ofthe skin, therebyincreasing the percentage of tanning metallic oxid.

.I'claim as my invention I 1. The herein described process (of tanningskins and hides by means of metallic salts, which consists inimpregnatin the prepared skins and hides wlth the so ution of a basicsalt .of a sesquioxid, and then treating the impregnated skins and hideswith the alkaline solution of another metallic oxidinsoluble in water. i1 2. The herein described im rovement in the art of tanning skins andhides by means nating the pre ared skins and hideswit the solution of aasic salt of a sesquioxid, and then treating the impregnated skins. and

hides with the alkaline solution of another metallic .oxid of theformulalMeO insoluble inwater.v

3. The herein described'im provement in the art-of tanningskins andhides by means of metallic salts, which consists in impregnating theprepared skins and'- hides with the solution of a basic salt of asesquioxid, and then treating the impregnated skins and hides with analkallne solution of sodiumzincate. v

5 4. The herein described improvement in, the art of tanning skins andhides by means of metallic salts, which consists in impregnating theprepared skins and hides with the solution of a basic salt of asesquioxid, and then treating the impregnated skins with the alkalinesolution of another metallic oxid insoluble in water in which a solubleoil is dissolved.

In testimony whereof I have hereunto set my hand in presence of twosubscribing witnesses.

' I HENRY SCHMID.

Witnesses:

W. A. LEONARD,- WILH. Gonna.

